Ingestion of vegetables containing heavy metals is one of the main ways in which these elements enter the human body. Once entered, heavy metals are deposited in bone and fat tissues, overlapping noble minerals. Slowly released into the body, heavy metals can cause an array of diseases. This study aimed to investigate the concentrations of cadmium, nickel, lead, cobalt and chromium in the most frequently consumed foodstuff in the São Paulo State, Brazil and to compare the heavy metal contents with the permissible limits established by the Brazilian legislation. A value of intake of heavy metals in human diets was also calculated to estimate the risk to human health. Vegetable samples were collected at the São Paulo General Warehousing and Centers Company, and the heavy metal content was determined by atomic absorption spectrophotometry. All sampled vegetables presented average concentrations of Cd and Ni lower than the permissible limits established by the Brazilian legislation. Pb and Cr exceeded the limits in 44 % of the analyzed samples. The Brazilian legislation does not establish a permissible limit for Co contents. Regarding the consumption habit of the population in the São Paulo State, the daily ingestion of heavy metals was below the oral dose of reference, therefore, consumption of these vegetables can be considered safe and without risk to human health.

Abstract:A conceptual model of water and solute transport pathways was developed and applied to a pasture hillslope in the southwestern Brazilian Amazon basin using select field measurements. Infiltration-excess or Horton overland flow (HOF), saturation overland flow (SOF), and groundwater in both the near-stream zone and upslope were sampled on a hillslope draining a 3Ð9 hectare pasture for a total of ten storms during the first half of the rainy season (October-November) in 2002. A Soil Conservation Service SCS curve number model of HOF and an annual water balance of both upslope and near-stream zones were used to calculate the contribution of each flowpath to solute export. HOF occurred in rainstorms greater than 5 mm and accounted for ¾8% of annual rainfall. Flow generated in the near-stream zone was ¾8% of annual rainfall. Sub-surface flow from upslope groundwater dominated annual runoff (¾19-30% of annual rainfall). Solutes fell into three categories according to flowpath. HOF from upslope positions dominated the export of total phosphorus (TP) and total dissolved phosphorus (TDP, 51-72% of total annual export). The near-stream zones controlled the export of K (58-65%), total dissolved nitrogen (TDN, 76-80%), and total nitrogen (TN, ¾75%) owing to relatively high solute concentrations and the large volume of water that flowed through the near-stream zone. Na and Si export was via groundwater from upslope (50-67% of annual export). The flux calculations were based on a small number of storms and are preliminary estimates designed to identify broad patterns in solute export via different hydrologic pathways. Additional processes, especially N removal at the groundwater-stream interface and in the stream channel, may affect actual export rates at the watershed scale. Whereas HOF production is negligible in Amazon forests, it represents a significant pathway for additional loss of elements, especially phosphorus, from mature pasture systems. The evidence presented here shows that biogeochemical perturbations and enhanced solute fluxes continue for decades following deforestation for pasture.

Resumo -O objetivo deste trabalho foi definir a melhor dose e época de aplicação, e a eficiência de utilização do N, utilizando-se uréia marcada com 15 N, pelo milho cultivado sob plantio direto, em sucessão à crotalária (Crotalaria juncea), ao milheto (Pennisetum americanum) e à vegetação espontânea (pousio), em um Latossolo Vermelho no Cerrado. O delineamento experimental foi o de blocos ao acaso, com 24 tratamentos e quatro repetições, em esquema fatorial incompleto, 3x3x2 + 6: três doses de N (80, 130 e 180 kg ha -1 ); três sistemas de cobertura do solo (crotalária, milheto e pousio); duas épocas de aplicação do N (estádio quatro ou oito folhas); e seis tratamentos adicionais (três sem aplicação de N e três que receberam 30 kg ha -1 de N na semeadura). O cultivo do milho em sucessão à crotalária proporciona maior quantidade na planta e aproveitamento pela planta do N proveniente do fertilizante e maior produtividade de grãos. A aplicação do N ao milho com quatro folhas proporciona maior produtividade de grãos, comparada à aplicação com oito folhas, quando em sucessão ao milheto.Termos para indexação: Zea mays, fertilizante 15 N, pousio, adubo verde, Cerrado, plantio direto. Nitrogen management in corn under no-tillage with different cover crops in a Rhodic Hapludox soilAbstract -The objective of this work was to evaluate the best rate and time for N application, and N utilization using urea-15 N, by corn crop grown under no-tillage system, in succession to sun hemp (Crotalaria juncea L.), millet (Pennisetum americanum) and to the spontaneous vegetation (fallow ground), in a Rhodic Hapludox soil in Cerrrado. The experimental design was randomized complete blocks, with 24 treatments and four replications, in an incomplete factorial 3x3x2 + 6: three N rates (80, 130 and 180 kg ha -1 N); three preceding cover crops (sun hemp, millet and fallow ground); two N application time (four leaves or eight leaves stage); and six additional treatments (three without N application and three that received 30 kg ha -1 N at seeding). The corn grown in succession to sun hemp provided higher amount of N derived from fertilizer, N utilization efficiency and grain yield. Application of N to corn four leaves stage provides higher grain yield, compared to the application to eight leaves stage, in succession to millet.

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RESUMO O cultivo de adubos verdes na entressafra altera a dinâmica e a recuperação do nitrogênio pelo milho no sistema solo-planta. O objetivo deste trabalho foi avaliar a eficiência de utilização do N da crotalária (Crotalaria juncea) e do milheto (Pennisetum INTRODUÇÃOO não revolvimento do solo e o cultivo de plantas de cobertura promovem modificações na ciclagem dos nutrientes, sendo o nitrogênio (N) o mais afetado, principalmente devido à decomposição mais lenta dos resíduos vegetais deixados na superfície do

Given their potential for biological nitrogen fixation, legumes used as green manure are an alternative source of nitrogen to crops, and can supplement or even replace mineral nitrogen fertilization. The utilization of nitrogen by sugarcane (Saccharum spp.) fertilized with sunn hemp (Crotalaria juncea L.) and ammonium sulphate (AS) was evaluated using the ), isotopic abundance of N (atoms % 15 N) in leaf +3 samples, and sugarcane productivity were used to calculate cumulative N, nitrogen in the plant derived from the fertilizer-Ndff (% and kg ha -1 ), as well as percent recovery of fertilizer N (R%). Sugarcane was analysed and pol and total recovered sugar calculated. The highest Ndff percentages were observed eight months after sugarcane planting for treatments containing green manure without mineral N, and green manure with mineral N, at 15.3 and 18.4%, respectively. The best nitrogen recovery was observed during harvest, 18 months after planting; the treatment containing mineral fertilizer showed 34.4% recovery, while the sum between mineral N plus green manure N showed 40.0%. Treatments containing green manure plus mineral N changed soil attributes, by increasing Ca and Mg contents, sum of bases, pH, and base saturation, and decreasing potential acidity. In the plant, those treatments increased Ca and K contents. ) e da abundância isotópica de N (% em átomos de 15 N) das amostras de folhas +3 e da produtividade da cana-de-açúcar, foram calculados o N-acumulado, nitrogênio na planta proveniente do fertilizante-NPPF (% e kg ha -1), e a recuperação percentual do N do fertilizante (%R). Foram realizadas análises tecnológicas da cana e calculados o pol (%) e açúcares totais recuperados. As maiores porcentagens de NPPF foram encontradas após oito meses de plantio da cana para os tratamentos com adubo verde sem N-mineral e adubo verde com N-mineral, respectivamente 15,3 e 18,4%. A maior recuperação do nitrogênio foi encontrada na colheita, dezoito meses após o plantio, sendo que o tratamento com fertilizante mineral apresentou 34,4% e na soma N-mineral mais N-adubo verde apresentou 40,0%. Os tratamentos com adubo verde mais N-mineral alteraram atributos do solo e da planta, promovendo aumento nos teores de Ca e Mg, soma de bases e saturação de bases e pH, com declínio na acidez potencial no solo, bem como aumento nos teores de Ca e K na parte aérea. Palavras-chave: Saccharum spp., crotalária júncea,

Natural abundance of tSN (6 tSN) of leaves harvested from tropical plants in Brazil and Thailand was analyzed. The 8 ~SN values of non-Nz-fixing trees in Brazil were +4.5 -+ 1.9%o, which is lower than those of soil nitrogen (+8.0-+2.2%0). In contrast, mimosa and kudzu had very low 6 ~SN values ( -1 . 4 -+ 0 . 5 % @ The t5 1-~N values of Panicum maximum and leguminous trees, except Leucaena leucocephala, were similar to those of non-N2-fixing trees, suggesting that the contribution of fixed N in these plants is negligible. The 6 15N values of non-N2-fixing trees in Thailand were +4.9 +_ 2.0%0. Leucaena leucocephala, Sesbania grandiflora, Casuarina spp. and Cycas spp. had low 6 tSN values, close to the value of atmospheric N 2 (0%e), pointing to a major contribution of N 2 fixation in these plants. Cassia spp. and Tamarindus indica had high 6 15N values, which confirms that these species are non-nodulating legumes. The 6 ~SN values of Acacia spp. and Gliricidia sepium and other potentially nodulating tree legumes were, on average, slightly lower than those of non-N2-fixing trees, indicating a small contribution of N 2 fixation in these legumes.

RESUMODesenvolveu-se, na Estação Experimental de Piracicaba -Instituto Agronômico (SAA-SP), de março/94 a setembro/95, um experimento para avaliar o potencial de fornecimento de nitrogênio de adubos, verde e mineral, aplicados, de forma exclusiva ou combinada, na cultura do milho. Em uma primeira fase, produziram-se, simultaneamente, mucuna-preta sem marcação isotópica no campo e adubo verde marcado com 15 N em casa de vegetação e, na segunda, a mucuna-preta foi incorporada ao solo, cultivando-se, em seguida, milho. O experimento constou dos seguintes tratamentos: testemunha, 15 N-mucuna-preta (4,4 t ha -1 de matéria seca e 25,8 g kg -1 de N), 15 N-uréia (50 e 100 kg ha -1 de N) e as possíveis combinações de mucuna-preta e uréia marcadas ou não com 15 N. Esses foram dispostos em delineamento experimental de blocos ao acaso com quatro repetições. O solo forneceu a maior parte do N acumulado nas plantas de milho, seguido, em ordem decrescente, pela uréia e mucuna-preta. A contribuição da uréia para o N acumulado nas plantas de milho foi proporcional à dose aplicada. O aproveitamento de nitrogênio da uréia pelo milho foi maior que o da mucunapreta, sendo os melhores efeitos proporcionados pela combinação das duas fontes. Termos de indexação:15 N, mucuna-preta, Mucuna aterrima, uréia, recuperação.